Vane-type separator

ABSTRACT

A vane-type separator with pockets for removing solid and liquid particles entrained in a gaseous stream. Vanes are fabricated from a plurality of modular sheet metal components which may be assembled to form vanes of varying lengths. The vanes further include pockets with rounded leading edges to encourage particulate to impinge on the vane and move into the pockets by surface tension. The device allows for a higher gas stream velocity before particulate is found downstream of the vane-type separator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 61/220,070 filed Jun. 24, 2009, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

This application generally relates to separators for removing solid and liquid particles suspended in gaseous streams and more specifically to improved vane structures allowing for increased gas velocity during separator operation.

BACKGROUND OF THE INVENTION

As is known, many chemical and industrial processes produce gaseous products which are removed via a gas stream. In addition to the gaseous products, solid particles or liquid droplets may be entrained within the gas stream. It is often desirable to remove entrained solid and liquid particulate from a gas stream in order to produce a pure gaseous product.

A vane separator is often used to remove solid and liquid particulate from a gaseous stream. Typically, vane separators consist of a plurality of undulated parallel plates that provide narrow zig-zag passageways through which a gas stream is forced. As a result, the flow of gas as well as the solid and liquid particulate rapidly changes direction several times. Solid and liquid particles have a higher density and mass than gas and are not able to rapidly change direction. As a result, particulate impinges on the vane structure and collects inside vane pockets.

Forcing gas through a vane separator at a high velocity or with a high particulate content may cause particulate to escape though the outlet of a vane separator. As a result, particulate may be found downstream of a vane separator and the gas stream will not be pure. The maximum operating characteristics of a vane separator with respect to variables such as gas velocity or particulate content before particulate is found downstream of the vane separator is known as “breakthrough.”

The narrow gaps between vanes, friction along vane surfaces and zig-zag configuration of a vane separator will often cause a drop in gas pressure from the inlet to the outlet. However, in many industrial and chemical applications of vane separators, it is desirable to minimize the pressure drop across a vane separator.

Furthermore, existing vane separators are limited in the amount of solid/liquid particulate that they are able to collect along a surface given a particular gas pressure, particulate content and vane configuration. As a result, it is desirable to provide collection of particulate while requiring a minimum of vanes.

Further still, vane separators are often used in offshore applications such as on oil platforms or the like. Offshore applications require that equipment weigh as little as possible to decrease transportation costs and increase safety in extreme weather conditions. As a result, it is desirable to minimize the weight of a vane separator. Furthermore, it is desirable to use fewer components and less welding in the fabrication of vane separators in order to decrease manufacturing costs.

It is therefore an objective of the present invention to provide a lightweight vane separator enabled to provide improved collection of solid and liquid particulate while minimizing the gas pressure drop from the inlet to the outlet.

A review of the prior art reveals that a number of technologies have been used in the past for removing solid and liquid particles from a gaseous stream. For example, U.S. Pat. No. 3,405,511 discloses a vane-type mist eliminator having pocket-like channels extending along the length of the vanes.

U.S. Pat. No. 3,405,511 teaches a vane type separator having a plurality of vane subassemblies wherein gas flows from the bottom to the top.

U.S. Pat. No. 1,928,706 discloses a mist extractor unit consisting of a plurality of vertical zig-zag vanes that are provided with extensions for the purpose of creating pockets to entrap liquid particulate collected by the vertical vanes.

U.S. Pat. No. 3,517,486 teaches a vane-type separator having a plurality of vane subassemblies clamped together by bolts to separate particulate from a gas stream.

Other references include U.S. Pat. No. 2,973,056 which describes passing gas through a filter and U.S. Pat. No. 3,358,580 which describes arcuate separating traps.

While the prior art may provide a partial solution, each are limited in various ways as briefly described below.

In particular, past systems may be limited as they do not suggest or teach the advantages of having rounded leading edges on a particulate collecting pocket or a modular vane design without a continuous steel base strip.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a vane separator for removing particulate entrained in a gas stream which comprises a plurality of parallel undulated vanes forming gas stream passages wherein:

-   -   i. each vane is formed from a plurality of sheet metal         components;     -   ii. each sheet metal component is connected to adjacent sheet         metal components;     -   iii. sheet metal components may be assembled in different         combinations to form vanes of varying lengths; and     -   iv. each vane includes a plurality of pockets for operatively         collecting particulate entrained within a gas stream wherein         each pocket has a rounded leading edge.

In a further embodiment, each vane includes a leading edge to add a pocket and provide improved gas flow.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described with reference to the accompanying figures in which:

FIG. 1 shows a series of parallel vanes in a preferred embodiment of the present invention having a leading edge.

FIG. 2 shows a series of parallel vanes in a preferred embodiment of the present invention without a leading edge.

FIG. 3 shows a conventional vane type demister in accordance with the prior art.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “particulate” refers to any solid particles or any liquid droplets that may be found within a gas stream.

As used herein, the term “liquid carryover” refers to finding particulate downstream of a vane separator.

As used herein, the term “breakthrough” refers to the maximum operating characteristics of a vane separator such as gas velocity or particulate content before liquid carryover occurs.

Overview

With reference to the figures, the present invention generally relates to a vane separator or demister 10 for the removal of liquid or solid particles from a gas stream. The device is particularly useful for removing particulate from various gases in chemical plants, petro-chemical plants, power generation plants and gas production, transmission and distribution systems. In accordance with known systems, the vane separator 10 generally includes a plurality of undulated vanes 16 arranged in parallel to form one or more gas passageways with inlets 12 and outlets 14.

Vanes are typically oriented horizontally and the gas stream travels from the inlet 12 to the outlet 14 as shown in FIGS. 1-2. The gas stream enters the vanes through the inlet and the undulations force the gas stream to take a tortuous path, whereby the entrained liquid droplets impinge and cling to the vanes. The liquid droplets will be forced into the pockets 22 by the gas pressure and may subsequently be removed from the vane separator.

Vane Fabrication and Design

As shown in FIGS. 1-2 vanes 16 are generally made of a plurality of modular sheet metal components 24. Each sheet metal component may be connected to adjacent sheet metal components to form vanes of different lengths. The modular sheet metal components may be attached together using a variety of known attachment methods such as welding or bolting.

As shown in FIG. 3, conventional vane separators 50 are comprised of a plurality of parallel vanes 52. Vanes 52 are formed from a base strip of sheet metal 54 to which a plurality of metal vane extensions 56 are attached to form pockets 58. The vanes 52 are undulated to encourage liquid droplets of impinge on the vanes and collect in the pockets. Metal components may be attached to the base sheet metal strip 54 by welding or other methods known to one of skill in the art.

Referring back to FIGS. 1-2, the present invention does not require a steel base strip for the operative attachment of metal vane extensions. As a result, the elimination of the steel base strip reduces the amount of metal required to fabricate a vane 16 thereby decreasing the weight of a vane separator 10. Furthermore, the removal of the metal base strip allows for an increased pocket 22 size thereby allowing for increased particulate collection. It is estimated that the monetary savings created by a design without a metal base strip is 20% less than conventional vane separator designs given current material costs.

In order to provide improved particulate collection, the present invention includes a rounded leading edge 20 at the edge of each pocket 22. As small liquid droplets impinge on a vane surface, the droplets will move towards a pocket 22 while remaining attached to the vane surface by surface tension. A rounded leading edge 20 encourages water droplets to move inside a pocket where they may be collected. Without a rounded leading edge, water droplets may not become entrapped within a pocket 22 and instead be re-entrained in the gas stream.

With reference to FIG. 1, a preferred embodiment of the present invention includes a leading edge 18 at the upstream end of each vane to direct the flow of gas into the vane separator 10 and create an additional pocket 22. Leading edges 18 further reduce gas turbulence, friction and allow for higher gas velocities within the vane separator 10. A leading edge 18 does not add a significant amount of weight to a vane separator 10.

With reference to FIG. 2, an alternate embodiment of the present invention is shown without a leading edge 18 at the inlet 12 to a vane separator 18.

As is known in the art, welding requires a significant amount of time and expense in the fabrication process for vane separators. Conventional vane separators such as those disclosed by U.S. Pat. No. 3,405,511 require spot or seam welding in 9 different places. Conversely, the present invention only requires welding in 7 places. The reduced number of welds in the present invention provides increase cost savings and decrease manufacturing time. It is estimated that the present invention requires 22% less welding in the fabrication process than conventional vane separators.

COMPARISON EXAMPLES

To create comparisons between the present invention and the prior art, a conventional vane separator and vane separators as shown in FIG. 1 of identical size were used. A mixture of air and water was used as the test stream and a 5 HP Variable Frequency Drive (VFD) blower was used to control air speed. Water was introduced into the test stream at 1000 psi through a plurality of nozzles that could be individually enabled or disabled. More specifically, the nozzles were atomizing type nozzles with a 0.006 inch orifice. The mist produced by the nozzles was observed to be very fine with a predicted particle size between 1 micron and 30 microns.

The testing protocol included increasing the velocity of the gas stream until breakthrough occurred. The gas velocity at which breakthrough occurred was determined by measuring the solid/liquid particle size of particulate using a Filtersense model LM 70 liquid mist monitor located downstream of the vane separator. The testing protocol further included taking a time dependant sample at a collection point at the outlet of the wind tunnel. Moreover, the pressure differential between the inlet and outlet of a vane separator was measured using a manometer. The gas velocity was measured using a Omega Engineering FMA-906-V flow measurement probe.

When compared to conventional vane separators and while using a low liquid to gas ratio, the present invention allows for an overall gas inlet velocity increase of 6% before breakthough. With an increased liquid to gas ratio, the present invention allowed for a 21% increase of gas velocity in comparison with conventional vane separators.

When analyzing the pressure differential between the inlet and outlet of a vane separator, the present invention and conventional vane separators showed comparable pressure drops across the device.

When compared with conventional vane separators of the same dimensions and made from the same materials, the present invention is 19% lighter than conventional vane separators.

Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art. 

1. A vane separator for removing particulate entrained in a gas stream which comprises: a) a plurality of parallel undulated vanes forming gas stream passages wherein: i) each vane is formed from a plurality of sheet metal components; ii) each sheet metal component is connected to adjacent sheet metal components; iii) sheet metal components may be assembled in different combinations to form vanes of varying lengths; and iv) each vane includes a plurality of pockets for operatively collecting particulate entrained within a gas stream wherein each pocket has a rounded leading edge.
 2. The vane separator as in claim 1 wherein the vane includes a leading edge.
 3. The vane separator as in claim 2 wherein the leading edge is a rounded leading edge. 